Method of preparing diisocyanate composition and optical lens

ABSTRACT

In the embodiments, an aqueous hydrochloric acid solution instead of hydrogen chloride gas and solid triphosgene instead of phosgene gas may be used in the process of preparing a diisocyanate from a diamine through a diamine hydrochloride. In addition, the embodiments provide processes for preparing a diisocyanate composition and an optical lens of higher quality by controlling the water content in the diamine hydrochloride composition for preparing a diisocyanate within a specific range.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent application Ser. No. 17/111,891 filed on Dec. 4, 2020, which claims priority of Korean patent application number 10-2019-0161540 filed on Dec. 6, 2019. The disclosure of each of the foregoing applications is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments relate to processes for preparing a diisocyanate composition and an optical lens. More specifically, the embodiments relate to a process for preparing a diisocyanate composition using a diamine hydrochloride composition, and a process for preparing an optical lens using the diisocyanate composition.

BACKGROUND ART

Isocyanates used as a raw material for plastic optical lenses are prepared by a phosgene method, a non-phosgene method, a pyrolysis method, or the like.

In the phosgene method, an amine as a raw material is reacted with phosgene (COCl₂) gas to synthesize an isocyanate. In addition, in the non-phosgene method, xylylene chloride is reacted with sodium cyanate in the presence of a catalyst to synthesize an isocyanate. In the pyrolysis method, an amine is reacted with an alkyl chloroformate to prepare a carbamate, which is pyrolyzed in the presence of a catalyst at a high temperature to synthesize an isocyanate.

The phosgene method among the above methods for preparing isocyanates is the most widely used. In particular, a direct method in which an amine is directly reacted with phosgene gas has been commonly used. But it has a problem that a plurality of apparatuses for the direct reaction of phosgene gas are required. Meanwhile, in order to supplement the direct method, a hydrochloride method has been developed in which an amine is reacted with hydrogen chloride gas to obtain an amine hydrochloride as an intermediate, which is reacted with phosgene, as disclosed in Korean Patent Publication No. 1994-0001948.

In the method of obtaining hydrochloride as an intermediate by reacting an amine with hydrogen chloride gas among the conventional phosgene methods for synthesizing isocyanates, a hydrochloride is produced as fine particles at atmospheric pressure, so that the agitation inside the reactor is not smoothly carried out. Thus, an additional process of raising the temperature to increase the pressure inside the reactor is required, and there is a problem that the yield of the final product is low as well.

In addition, phosgene gas used in the conventional phosgene method is highly toxic and is a substance subject to environmental regulations. There is a difficulty in storage and management since a separate cooling apparatus is required to store it.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

Accordingly, the present inventors were able to solve the conventional environmental, yield, and quality problems in the process of preparing a diisocyanate, which is mainly used as a raw material for plastic optical lenses, from a diamine through a hydrochloride thereof by way of using an aqueous hydrochloric acid solution instead of hydrogen chloride gas and solid triphosgene instead of phosgene gas while adjusting the reaction conditions.

In addition, the present inventors have focused that if the b* value according to the CIE color coordinate of a diisocyanate composition falls outside a specific range, it has an impact on the stria, transmittance, yellow index, and refractive index of the final optical lens. In addition, the present inventors have discovered that, in the process of preparing a diamine hydrochloride, which is used as a raw material for the synthesis of a diisocyanate, Fe ions in the aqueous hydrochloric acid solution are reacted with the diamine to increase the b* value of the diamine hydrochloride composition, thereby increasing the b* value of the diisocyanate composition.

Accordingly, an object of the embodiment is to provide a diisocyanate composition in which the b* value according to the CIE color coordinate is adjusted within a specific range, a process for preparing the same, and a process for preparing an optical lens of high quality using the same.

Solution to the Problem

According to an embodiment, there is provided a process for preparing a diisocyanate composition, which comprises (1) reacting a diamine composition with an aqueous hydrochloric acid solution to obtain a diamine hydrochloride composition; and (2) reacting the diamine hydrochloride composition with triphosgene to obtain a diisocyanate composition, wherein the diisocyanate composition has a b* value according to the CIE color coordinate of 0.1 to 2.0.

According to another embodiment, there is provided a process for preparing an optical lens, which comprises (1) reacting a diamine composition with an aqueous hydrochloric acid solution to obtain a diamine hydrochloride composition; (2) reacting the diamine hydrochloride composition with triphosgene to obtain a diisocyanate composition; and (3) mixing the diisocyanate composition with a thiol or an episulfide and polymerizing and curing the resultant in a mold, wherein the diisocyanate composition has a b* value according to the CIE color coordinate of 0.1 to 2.0.

According to still another embodiment, there is provided a diisocyanate composition, which has a b* value according to the CIE color coordinate of 0.1 to 2.0.

Advantageous Effects of the Invention

In the process for preparing a diisocyanate according to the above embodiment, phosgene gas, which is highly toxic and has difficulties in storage and management, is not used. Instead, triphosgene, which is less toxic and does not require a separate cooling storage apparatus since it is solid at room temperature, is used; thus, it is excellent in the handling convenience and processability. In addition, in the process for preparing a diisocyanate according to the above embodiment, an aqueous hydrochloric acid solution, without the use of hydrogen chloride gas, is used to prepare a diamine hydrochloride as an intermediate. Since the reaction can be carried out even at atmospheric pressure, an additional apparatus for high-temperature heating and cooling is not required, and the yield can be enhanced.

In addition, in the process for preparing a diisocyanate composition according to the above embodiment, an aqueous hydrochloric acid solution is used to prepare a diamine hydrochloride composition, so that the final yield can be further enhanced. The selection of raw materials can be broadened since the content of water and impurities in the raw material diamine has little impact.

In particular, according to the above embodiment, the b* value according to the CIE color coordinate of a diisocyanate composition is adjusted within a specific range, thereby improving the stria, transmittance, yellow index, and refractive index of the final optical lens prepared using the same. In addition, in the process of preparing a diamine hydrochloride, which is used as a raw material for the synthesis of a diisocyanate, an aqueous hydrochloric acid solution containing a specific content of Fe ions is used, or the diamine hydrochloride composition is washed, whereby it is possible to adjust the b* value of the diamine hydrochloride composition.

Thus, the process for preparing a diisocyanate composition according to the embodiment can be applied to the preparation of a plastic optical lens of high quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B schematically show the process for preparing a diisocyanate composition according to an embodiment.

FIG. 2 shows an example of the process equipment for the reaction of a diamine hydrochloride and triphosgene.

REFERENCE NUMERALS OF THE DRAWINGS

-   -   T-1: first tank, T-2: second tank, T-3: third tank     -   R-1: reactor, D-1: first distiller, D-2: second distiller     -   C-1: first condenser, C-2: second condenser, C-3: third         condenser     -   S-1: first scrubber, S-2: second scrubber     -   G-1: viewing window, V-1: solvent recovery apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

Throughout the present specification, when a part is referred to as “comprising” an element, it is understood that other elements may be comprised, rather than other elements are excluded, unless specifically stated otherwise.

In addition, all numbers and expression related to the physical properties, contents, dimensions, and the like used herein are to be understood as being modified by the term “about,” unless otherwise indicated.

In the present specification, an “amine” refers to a compound having one or more amine groups at the terminal, and a “diamine” refers to a compound having two amine groups at the terminal. They may have a wide variety of structures depending on the skeleton of an aliphatic chain, an aliphatic ring, and an aromatic ring. Specific examples of the diamine include xylylenediamine (XDA), hexamethylenediamine (HDA), 2,2-dimethylpentanediamine, 2,2,4-trimethylhexanediamine, butenediamine, 1,3-butadiene-1,4-diamine, 2,4,4-trimethylhexamethylenediamine, bis(aminoethyl)carbonate, bis(aminoethyl) ether, bis(aminoethyl)benzene, bis(aminopropyl)benzene, α,α,α′,α′-tetramethylxylylenediamine, bis(aminobutyl)benzene, bis(aminomethyl)naphthalene, bis(aminomethyl)diphenyl ether, bis(aminoethyl)phthalate, 2,6-di(aminomethyl)furan, hydrogenated xylylenediamine (H6XDA), dicyclohexylmethanediamine, cyclohexanediamine, methylcyclohexanediamine, isophoronediamine (IPDA), dicyclohexyldimethylmethanediamine, 2,2-dimethyldicyclohexylmethanediamine, 2,5-bis(aminomethyl)bicyclo-[2,2,1]-heptane, 2,6-bis(aminomethyl)bicyclo-[2,2,1]-heptane, 3,8-bis(aminomethyl)tricyclodecane, 3,9-bis(aminomethyl)tricyclodecane, 4,8-bis(aminomethyl)tricyclodecane, 4,9-bis(aminomethyl)tricyclodecane, norbornenediamine (NBDA), bis(aminomethyl) sulfide, bis(aminoethyl) sulfide, bis(aminopropyl) sulfide, bis(aminohexyl) sulfide, bis(aminomethyl) sulfone, bis(aminomethyl) disulfide, bis(aminoethyl) disulfide, bis(aminopropyl) disulfide, bis(aminomethylthio)methane, bis(aminoethylthio)methane, bis(aminoethylthio)ethane, and bis(aminomethylthio)ethane. More specifically, the diamine may be at least one selected from the group consisting of xylylenediamine (XDA), norbornenediamine (NBDA), hydrogenated xylylenediamine (H6XDA), isophoronediamine (IPDA), and hexamethylenediamine (HDA). The xylylenediamine (XDA) includes orthoxylylenediamine (o-XDA), metaxylylenediamine (m-XDA), and paraxylylenediamine (p-XDA).

In the present specification, an “isocyanate” refers to a compound having an NCO group, a “diisocyanate” refers to a compound having two NCO groups at the terminal. They may have a wide variety of structures depending on the skeleton of an aliphatic chain, an aliphatic ring, and an aromatic ring. Specific examples of the diamine include xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), 2,5-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane, 2,6-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane, hydrogenated xylylene diisocyanate (H6XDI), dicyclohexylmethane diisocyanate, isophorone diisocyanate (IPDI), 1,2-diisocyanatobenzene, 1,3-diisocyanatobenzene, 1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene, ethylphenylene diisocyanate, dimethylphenylene diisocyanate, biphenyl diisocyanate, toluidine diisocyanate, 4,4′-methylenebis(phenylisocyanate), 1,2-bis(isocyanatomethyl)benzene, 1,3-bis(isocyanatomethyl)benzene, 1,4-bis(isocyanatomethyl)benzene, 1,2-bis(isocyanatoethyl)benzene, 1,3-bis(isocyanatoethyl)benzene, 1,4-bis(isocyanatoethyl)benzene, α,α,α′,α′-tetramethylxylylene diisocyanate, bis(isocyanatomethyl)naphthalene, bis(isocyanatomethylphenyl) ether, norbornene diisocyanate (NBDI), bis(isocyanatomethyl) sulfide, bis(isocyanatoethyl) sulfide, bis(isocyanatopropyl) sulfide, 2,5-diisocyanatotetrahydrothiophene, 2,5-diisocyanatomethyltetrahydrothiophene, 3,4-diisocyanatomethyltetrahydrothiophene, 2,5-diisocyanato-1,4-dithiane, and 2,5-diisocyanatomethyl-1,4-dithiane. More specifically, the diisocyanate may be at least one selected from the group consisting of xylylene diisocyanate (XDI), norbornene diisocyanate (NBDI), hydrogenated xylylene diisocyanate (H6XDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI). The xylylene diisocyanate (XDI) includes orthoxylylene diisocyanate (o-XDI), metaxylylene diisocyanate (m-XDI), and paraxylylene diisocyanate (p-XDIA).

In the present specification, as is well known, a “composition” may refer to a form in which two or more chemical components are mixed or combined in a solid, liquid, and/or gas phase while generally maintaining their respective unique properties.

The compounds used in each reaction step according to the above embodiment (e.g., triphosgene) or the compounds obtained as a result of the reaction (e.g., diamine hydrochloride, diisocyanate) are generally present in a mixed or combined state with heterogeneous components produced as unreacted raw materials in each reaction step, as side reactions or reaction with water, or as natural decomposition of the compounds. A trace amount of these components may remain to exist with the main components.

According to the embodiment, since attention is paid to these heterogeneous components mixed or combined with the main compounds, even a trace amount of the heterogeneous components is treated as a composition mixed or combined with the main compounds to specifically illustrate the components and contents thereof.

In addition, in the present specification, for clear and easy distinction between various compositions, terms are also described in combination with the names of the main components in the composition. For example, a “diamine hydrochloride composition” refers to a composition comprising a diamine hydrochloride as a main component, and a “diisocyanate composition” refers to a composition comprising a diisocyanate as a main component. In such event, the content of the main component in the composition may be 50% by weight or more, 80% by weight or more, or 90% by weight or more, for example, 90% by weight to 99.9% by weight.

[Process for Preparing a Diisocyanate Composition]

The process for preparing a diisocyanate composition according to an embodiment comprises (1) reacting a diamine composition with an aqueous hydrochloric acid solution to obtain a diamine hydrochloride composition; and (2) reacting the diamine hydrochloride composition with triphosgene to obtain a diisocyanate composition, wherein the diisocyanate composition has a b* value according to the CIE color coordinate of 0.1 to 2.0.

FIG. 1 schematically shows the process for preparing a diisocyanate composition according to an embodiment. In FIG. 1, R comprises an aromatic ring, an aliphatic ring, an aliphatic chain, and the like. As a specific example, R may be xylylene, norbornene, hydrogenated xylylene, isophorone, or hexamethylene, but it is not limited thereto.

Hereinafter, each step will be described in detail.

Preparation of a Diamine Hydrochloride Composition

First, a diamine is reacted with an aqueous hydrochloric acid solution to obtain a diamine hydrochloride composition.

In addition, after the reaction of the diamine and the aqueous hydrochloric acid solution, a first organic solvent may be further added to obtain the diamine hydrochloride composition in a solid phase.

The following Reaction Scheme 1 shows an example of the reaction in this step.

In the above scheme, R comprises an aromatic ring, an aliphatic ring, an aliphatic chain, and the like. As a specific example, R may be xylylene, norbornene, hydrogenated xylylene, isophorone, or hexamethylene, but it is not limited thereto.

FIG. 1A and FIG. 1B schematically show the process for preparing a diisocyanate composition according to an embodiment. In FIG. 1A and FIG. 1B, R comprises an aromatic ring, an aliphatic ring, an aliphatic chain, and the like. As a specific example, R may be xylylene, norbornene, hydrogenated xylylene, isophorone, or hexamethylene, but it is not limited thereto.

In FIG. 1A, (i) may comprise a step of adding an aqueous hydrochloric acid solution to react a diamine with the aqueous hydrochloric acid solution. In FIG. 1A, (ii) may comprise at least one step selected from a precipitation step, a filtration step, a drying step, and a washing step. In FIG. 1B, (iii) may comprise a step of adding triphosgene to react a diamine hydrochloride composition with triphosgene. In FIG. 1B, (iv) may comprise at least one step selected from a degassing step, a filtration step, and a distillation step.

In the conventional method in which hydrogen chloride gas is used, a hydrochloride is produced as fine particles upon reaction at atmospheric pressure, so that the agitation inside the reactor is not smoothly carried out. Thus, an additional process of raising the pressure to increase the internal temperature of the reactor is required, and there is a problem that the yield of the final product is low as well.

According to the above embodiment, however, since an aqueous hydrochloric acid solution is used, it is possible to solve the problem involved in the prior art in which hydrogen chloride gas is used. Specifically, when an aqueous hydrochloric acid solution is used, the product obtained through the reaction is in a solid form rather than a slurry form, so that the yield is high. The reaction can be carried out even at atmospheric pressure, so that a separate apparatus or process for rapid cooling is not required.

The concentration of the aqueous hydrochloric acid solution may be 5% by weight to 50% by weight. Within the above concentration range, it is possible to minimize the dissolution of the hydrochloride in the aqueous hydrochloric acid solution, thereby enhancing the final yield, and to improve the handling convenience.

Specifically, the concentration of the aqueous hydrochloric acid solution may be 10% by weight to 45% by weight, 20% by weight to 45% by weight, or 30% by weight to 40% by weight. More specifically, the aqueous hydrochloric acid solution may have a concentration of 20% by weight to 45% by weight.

The diamine and the aqueous hydrochloric acid solution may be introduced to the reaction at an equivalent ratio of 1:2 to 5. If the equivalent ratio is within the above range, it is possible to reduce the unreacted materials and to prevent a decrease in the yield caused by dissolution as water is generated. Specifically, the diamine and the aqueous hydrochloric acid solution may be introduced to the reaction at an equivalent ratio of 1:2 to 2.5.

The introduction of the diamine and the aqueous hydrochloric acid solution may be carried out while the internal temperature of the reactor is maintained to be constant. When the diamine and the aqueous hydrochloric acid solution are introduced, the internal temperature of the reactor may be in the range of 20° C. to 100° C. Within the above temperature range, it is possible to prevent the temperature from being raised above the boiling point, which is not suitable for the reaction, or the temperature from being lowered too much, whereby the reaction efficiency is reduced. Specifically, when the diamine and the aqueous hydrochloric acid solution are introduced, the internal temperature of the reactor may be 20° C. to 60° C., more specifically 20° C. to 40° C. or 40° C. to 60° C.

In the conventional hydrochloride method, a large amount of heat is generated in the reaction, which requires rapid cooling through a separate cooler, whereas the reaction materials are introduced while a low temperature is maintained according to the embodiment, which does not require a separate cooler.

The introduction of the diamine and the aqueous hydrochloric acid solution may be carried out, for example, in a sequence in which the aqueous hydrochloric acid solution may be first introduced to the reactor and the diamine may then be slowly introduced to the reactor. The introduction of the diamine and/or the aqueous hydrochloric acid solution may be carried out for 30 minutes to 3 hours.

When the introduction of the diamine and the aqueous hydrochloric acid solution is completed, the internal temperature of the reactor may be lowered to 0° C. to 20° C., 0° C. to 10° C., or 10° C. to 20° C.

The reaction between the diamine and the aqueous hydrochloric acid solution may be carried out at atmospheric pressure for, for example, 30 minutes to 2 hours with stirring.

As a result of the reaction between the diamine and the aqueous hydrochloric acid solution, a diamine hydrochloride composition in an aqueous solution form may be obtained as the reaction resultant.

Thereafter, a step of treating the diamine hydrochloride composition may be further carried out. For example, the step of treating the diamine hydrochloride composition may comprise at least one of precipitating the diamine hydrochloride composition, filtering the diamine hydrochloride composition, drying the diamine hydrochloride composition, and washing the diamine hydrochloride composition.

Specifically, a first organic solvent may be introduced to the reaction resultant to precipitate a solid diamine hydrochloride composition. That is, the first organic solvent may induce the precipitation of a solid diamine hydrochloride composition through crystallization. More specifically, the first organic solvent may be introduced to the reaction resultant, which is cooled and further stirred to carry out the reaction.

Specifically, the first organic solvent may be at least one selected from the group consisting of diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran, methanol, ethanol, dimethyl sulfoxide, dimethylformamide, acetonitrile, acetone, trichloroethylene, tetrachloroethane, trichloroethanol, n-butanol, isobutanol, methyl ethyl ketone, methyl butyl ketone, isopropanol, hexane, chloroform, and methyl acetate.

The amount (weight) of the first organic solvent introduced may be 1 to 5 times the weight of the diamine. If the introduced amount is within the above range, it is possible to prevent the use of excessive organic solvents while the yield of the final hydrochloride is high. Specifically, the first organic solvent may be introduced to the reaction in an amount of 1 to 2 times, 1 to 1.5 times, or 1.3 to 1.5 times, the weight of the diamine.

After the first organic solvent is introduced, the cooling temperature may be −10° C. to 10° C. or −5° C. to 5° C. In addition, the additional reaction time after cooling may be 30 minutes to 2 hours or 30 minutes to 1 hour.

According to a specific example, the steps of (1a) introducing the aqueous hydrochloric acid solution to a first reactor; (1b) introducing the diamine to the first reactor and stirring them; and (1c) introducing the first organic solvent to the first reactor and stirring them may be sequentially carried out.

More specifically, the process may further comprise cooling the inside of the reactor to a temperature of 0° C. to 10° C. after the introduction of the diamine and before stirring in step (1b); and cooling the inside of the reactor to a temperature of −5° C. to 5° C. after the introduction of the first organic solvent and before stirring in step (1c).

After the first organic solvent is introduced, separation, filtration, washing, and drying may be further carried out. For example, after the first organic solvent is introduced, the aqueous layer may be separated, filtered, washed, and dried to obtain a solid diamine hydrochloride composition. The washing may be carried out one or more times using, for example, a solvent having a polarity of 5.7 or less. In addition, the drying may be carried out using vacuum drying. For example, it may be carried out at a temperature of 40° C. to 90° C. and a pressure of 2.0 torr or less.

As a result, the impurities generated in the step of obtaining the diamine hydrochloride composition may be removed together with the first organic solvent. Thus, the process may further comprise removing the impurities generated in the step of obtaining the diamine hydrochloride composition together with the first organic solvent. Impurities are generated in the reaction for preparing the diamine hydrochloride composition and are contained in the first organic solvent. Such impurities may be removed by the step of removing the first organic solvent, whereby the purity of the product may be increased.

According to the above process, a diamine is reacted with an aqueous hydrochloric acid solution, which is then subjected to additional treatment such as precipitation, filtration, drying, and washing, whereby a solid diamine hydrochloride composition can be obtained with high purity. In contrast, in the conventional process in which a diamine is reacted with hydrogen chloride gas in an organic solvent, a slurry of a diamine hydrochloride is obtained, which is not readily purified.

The yield of the diamine hydrochloride composition thus obtained may be 50% or more, 65% or more, 80% or more, 85% or more, or 90% or more, specifically 85% to 95% or 88% to 92%.

Meanwhile, the organic layer can be separated from the reactant and recycled as an organic solvent. Thus, the recovery rate of the first organic solvent may be 80% or more, 85% or more, or 90% or more, specifically 80% to 95% or 80% to 82%.

Diamine Hydrochloride Composition

In the process for preparing a diamine hydrochloride as described above, the diamine is easily deteriorated by temperature and humidity due to its high reactivity and pH, so that the b* value according to the CIE color coordinate of the diamine hydrochloride composition may be increased. In particular, if a diamine hydrochloride composition having a b* value of a certain level or higher is used to prepare a diisocyanate composition, the color and haze may be deteriorated, and it may have an impact on the stria, transmittance, yellow index, and refractive index of the final optical lens. In addition, if distillation is carried out several times in order to make a discolored diisocyanate composition colorless and transparent, it may cause a loss in yield, thereby decreasing the economic efficiency.

According to the above embodiment, however, the b* value according to the CIE color coordinate of the diamine hydrochloride composition in water may be adjusted, so that it is possible to enhance the optical characteristics of a diisocyanate composition and an optical lens.

The diamine hydrochloride composition prepared by the process according to the above embodiment has a b* value according to the CIE color coordinate of 1.5 or less or 1.2 or less when dissolved in water at a concentration of 8% by weight. For example, the b* value according to the CIE color coordinate may be 1.0 or less or 0.8 or less. Specifically, the b* value according to the CIE color coordinate may be 0.1 to 1.2, 0.1 to 1.0, 0.1 to 0.8, or 0.2 to 1.0.

In order to adjust the b* value of the diamine hydrochloride composition, an aqueous hydrochloric acid solution having a content of Fe ions at a certain level or less may be used as a raw material. For example, the content of Fe ions in the aqueous hydrochloric acid solution used for preparing the diamine hydrochloride composition may be 0.5 ppm or less. Specifically, the content of Fe ions in the aqueous hydrochloric acid solution may be 0.3 ppm or less or 0.2 ppm or less. More specifically, the content of Fe ions in the aqueous hydrochloric acid solution may be 0.001 ppm to 0.5 ppm or 0.1 ppm to 0.3 ppm.

Alternatively, the b* value according to the CIE color coordinate of the diamine hydrochloride composition may be adjusted by washing it with a solvent having a polarity of 5.7 or less. In such event, the solvent having a polarity of 5.7 or less may comprise dichloromethane, and other solvents may be used. In addition, the temperature of the solvent having a polarity of 5.7 or less may be 5° C. or lower, for example, 0° C. to 5° C.

That is, the process according to the embodiment may further comprise washing the diamine hydrochloride composition with a solvent having a polarity of 5.7 or less at 5° C. or lower.

In addition, the process according to the embodiment may further comprise measuring the b* value according to the CIE color coordinate of the diamine hydrochloride composition. If the b* value thus measured is greater than 1.5, the b* value of the diamine hydrochloride composition may be adjusted by repeating the above washing. As a result, the b* value according to the CIE color coordinate of the diamine hydrochloride composition may be adjusted to 1.5 or less when dissolved in water at a concentration of 8% by weight.

The diamine hydrochloride composition obtained by the above process mainly comprises a diamine hydrochloride, and the content of the diamine hydrochloride may be 85% by weight to 99.9% by weight based on the total weight of the composition. In such event, the diamine hydrochloride may contain two HCl bonded to the two terminal amine groups of the diamine.

In addition, the diamine hydrochloride composition may comprise Fe ions, and the content of Fe ions may be 10 ppm or less based on the total weight of the diamine hydrochloride composition.

In addition, the water content of the diamine hydrochloride composition thus obtained may be 5% or less. If it exceeds 5%, the physical properties of the lens finally prepared are not good.

Preparation of a Diisocyanate Composition

Next, the diamine hydrochloride composition is reacted with triphosgene to obtain a diisocyanate composition. In such event, the reaction of the diamine hydrochloride composition with triphosgene may be carried out in a second organic solvent.

The following Reaction Scheme 2 shows an example of the reaction in this step.

In the above scheme, R comprises an aromatic ring, an aliphatic ring, an aliphatic chain, and the like. As a specific example, R may be xylylene, norbornene, hydrogenated xylylene, isophorone, or hexamethylene, but it is not limited thereto.

Specifically, the diamine hydrochloride composition prepared above is introduced to a second organic solvent, reacted with triphosgene (BTMC, bis(trichloromethyl)carbonate), and then purified to obtain a diisocyanate composition.

Specifically, the second organic solvent may be at least one selected from the group consisting of benzene, toluene, ethylbenzene, chlorobenzene, monochlorobenzene, 1,2-dichlorobenzene (ODCB), dichloromethane, 1-chloro-n-butane, 1-chloro-n-pentane, 1-chloro-n-hexane, chloroform, carbon tetrachloride, n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, cyclopentane, cyclooctane, and methylcyclohexane.

The amount (weight) of the second organic solvent introduced may be 1 to 5 times the weight of the diamine hydrochloride composition. If the introduced amount is within the above range, it is possible to prevent the use of excessive organic solvents while the yield of the final diisocyanate is high. Specifically, the second organic solvent may be introduced to the reaction in an amount of 2 to 5 times or 3 to 5 times the weight of the diamine hydrochloride composition.

The reaction temperature of the diamine hydrochloride composition and triphosgene is 115° C. or higher, so that the reaction between the diamine hydrochloride and triphosgene is carried out more smoothly, which may be advantageous for increasing the yield and shortening the reaction time. In addition, if the reaction temperature of the diamine hydrochloride composition and triphosgene is 160° C. or less, it is possible to suppress the generation of impurities such as tar when the final diisocyanate is produced. For example, the reaction temperature of the diamine hydrochloride composition and triphosgene may be 115° C. to 160° C., 115° C. to 130° C., or 130° C. to 160° C.

In addition, if the reaction temperature of the diamine hydrochloride composition and triphosgene is 130° C. or lower, it may be more advantageous for suppressing impurities containing chlorine (e.g., chloromethylbenzyl isocyanate, 1,3-bis(chloromethyl)benzene, and the like). Specifically, the reaction temperature of the diamine hydrochloride composition and triphosgene may be 115° C. to 130° C. More specifically, the reaction temperature of the diamine hydrochloride composition and triphosgene may be 115° C. to 120° C.

The reaction of the diamine hydrochloride composition with triphosgene may be carried out for 5 hours to 100 hours. When the reaction time is within the above range, the reaction time is not excessive, and the production of unreacted materials due to the generation of phosgene can be minimized. Specifically, the reaction of the diamine hydrochloride composition with triphosgene may be carried out for 15 hours to 40 hours, 20 hours to 35 hours, or 24 hours to 30 hours.

As a specific example, the reaction of the diamine hydrochloride composition with triphosgene may be carried out at a temperature of 115° C. to 160° C. for 5 hours to 100 hours.

The diamine hydrochloride composition and triphosgene may be introduced to the reaction at an equivalent ratio of 1:1 to 5. When the equivalent ratio is within the above range, the reaction efficiency is high, and it is possible to prevent an increase in reaction time due to an excessive introduction. Specifically, the diamine hydrochloride composition and triphosgene may be introduced to the reaction at an equivalent ratio of 1:1.5 to 4 or 1:2 to 2.5.

The reaction of the diamine hydrochloride composition and triphosgene may sequentially comprise mixing the diamine hydrochloride composition with the second organic solvent to obtain a first solution; mixing triphosgene with the second organic solvent to obtain a second solution; and introducing the second solution to the first solution and stirring them.

In such event, the introduction of the second solution and stirring may be carried out at a temperature of 115° C. to 160° C. In addition, the introduction of the second solution may be divided into two or more times for a total of 25 hours to 40 hours. In addition, here, the time for each introduction may be 5 hours to 25 hours or 10 hours to 14 hours. In addition, the time for further reaction by stirring after the introduction may be 2 hours to 5 hours or 3 hours to 4 hours.

Alternatively, the reaction of the diamine hydrochloride composition and triphosgene may sequentially comprise (2a) introducing the second organic solvent to a second reactor; (2b) introducing the diamine hydrochloride composition to the second reactor and stirring them; and (2c) introducing triphosgene to the second reactor and stirring them.

In such event, the introduction of triphosgene in step (2c) may be carried out by introducing a solution in which triphosgene is dissolved in the same solvent as the second organic solvent to the reactor as divided into two or more times at a temperature of 115° C. to 130° C. for a total of 25 hours to 40 hours. In addition, here, the time for each introduction may be 5 hours to 25 hours or 10 hours to 14 hours. In addition, the time for further reaction by stirring after the introduction may be 2 hours to 5 hours or 3 hours to 4 hours.

Upon the reaction, the reaction resultant may be cooled at 90° C. to 110° C.

The resultant obtained through the reaction may be further subjected to separation, degassing, cooling, filtration, distillation, and the like.

For example, after the reaction, the reaction resultant may be subjected to degassing at 80° C. to 150° C. with the bubbling of nitrogen gas. In addition, after the degassing, it may be cooled to 10° C. to 30° C., and solids may be filtered off.

The diisocyanate composition may be obtained by distillation after the reaction of the diamine hydrochloride composition and triphosgene.

The distillation may comprise distillation to remove the second organic solvent. For example, after the reaction, the reaction resultant may be distilled at 40° C. to 60° C. for 2 hours to 8 hours to remove the second organic solvent. The pressure during the distillation may be 2.0 torr or less, 1.0 torr or less, 0.5 torr or less, or 0.1 torr or less. In addition, the second organic solvent may be recovered and recycled through the distillation.

In addition, the distillation may comprise distilling the diisocyanate. For example, the distillation may comprise distillation of diisocyanate at 100° C. to 130° C. If the distillation temperature is within the above range, it is more advantageous for preventing a deterioration in the physical properties of the final optical lens such as stria, cloudiness, and yellowing by effectively removing hydrolyzable chlorine compounds generated at high temperatures such as chloromethylbenzyl isocyanate (CBI) and 1,3-bis(chloromethyl)benzene. Specifically, the distillation may be carried out by setting the bottom temperature of the distiller to 100° C. to 130° C. For example, the distillation may be carried out by setting the reboiler temperature to 100° C. to 130° C. In addition, the pressure during the distillation may be 2.0 torr or less, 1.0 torr or less, 0.5 torr or less, or 0.1 torr or less. Specifically, the distillation may comprise distillation of diisocyanate at a temperature of 100° C. to 130° C. and a pressure of 2.0 torr or less.

In addition, the time for the distillation of diisocyanate may be 1 hour or more, 2 hours or more, or 3 hours or more, and may be 10 hours or less or 5 hours or less. Specifically, the distillation of diisocyanate may be carried out for 2 hours to 10 hours.

The yield of the distillation of diisocyanate may be 80% or more, specifically 85% or more, 87% or more, or 90% or more. In such event, the distillation yield may be calculated by measuring the amount of the diisocyanate composition upon the distillation relative to the theoretical amount of the diisocyanate composition produced from the amounts of the diamine hydrochloride composition introduced to the reaction with triphosgene.

According to the process of the above embodiment, the reaction temperature range of the diamine hydrochloride composition and triphosgene is controlled, whereby the crude diisocyanate composition before purification may contain very little impurities. Specifically, the diisocyanate composition may contain 99.0% by weight or more of the diisocyanate before the distillation of diisocyanate. In addition, the diisocyanate composition may contain 99.9% by weight or more of the diisocyanate after the distillation of diisocyanate.

In addition, the content of aromatic compounds having a halogen group in the diisocyanate composition may be 1,000 ppm or less.

In addition, the yield of the distillation of diisocyanate finally obtained may be 80% or more, 85% or more, or 90% or more.

Diisocyanate Composition

The diisocyanate composition prepared using a diamine hydrochloride composition and triphosgene as described above may be improved in terms of the color and haze.

In particular, the diisocyanate composition according to the above embodiment has a b* value according to the CIE color coordinate of 0.1 to 2.0. An optical lens prepared from the diisocyanate composition having a value of b* within the above range may have improved stria, transmittance, yellow index, and refractive index. Specifically, the b* value according to the CIE color coordinate of the diisocyanate composition may be 0.1 to 1.5, 0.1 to 1.2, 0.1 to 1.0, or 0.1 to 0.8.

In addition, the diisocyanate composition may have an APHA (American Public Health Association) color value of 20 or less or 10 or less. Specifically, the diisocyanate composition may have an APHA color value of 1 to 20 or 1 to 10.

In addition, the diisocyanate composition may have a haze of 10% or less, 5% or less, or 3% or less.

In addition, the content of diisocyanate in the diisocyanate composition may be 90% by weight or more, 95% by weight or more, 99.5% by weight or more, or 99.9% by weight or more, specifically 90% to 99.9% by weight.

In addition, the content of Fe ions in the diisocyanate composition may be 10 ppm or less, 5 ppm or less, or 1 ppm or less. Specifically, the content of Fe ions in the diisocyanate composition may be 0.2 ppm or less.

In addition, the diisocyanate composition may further comprise benzyl isocyanate, methylbenzyl isocyanate, cyanobenzyl isocyanate, and the like. The total content of these components may be about 1% by weight or less.

The diisocyanate composition may comprise xylylene diisocyanate or other diisocyanates used in the preparation of optical lenses. Specifically, it may comprise at least one selected from the group consisting of orthoxylylene diisocyanate (o-XDI), metaxylylene diisocyanate (m-XDI), paraxylylene diisocyanate (p-XDI), norbornene diisocyanate (NBDI), hydrogenated xylylene diisocyanate (H6XDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI).

According to the process of the above embodiment, the yield of diisocyanate is high, the recycling rate of organic solvents is excellent, it is environmentally friendly since highly toxic phosgene gas is not used, it is possible to react at atmospheric pressure, and a separate apparatus for pressurization or rapid cooling is not required.

Measurement of the Color and Transparency of a Reaction Solution

The step of obtaining a diisocyanate composition from the diamine hydrochloride composition and triphosgene may comprise (aa) reacting the diamine hydrochloride composition with triphosgene in a second organic solvent in a reactor to obtain a reaction solution; (ab) measuring the color and transparency of the reaction solution; and (ac) obtaining a diisocyanate composition from the reaction solution.

In the reaction of the diamine hydrochloride composition and triphosgene, the color and transparency of the reaction solution may be measured to adjust the reaction conditions.

For example, in the reaction of metaxylylenediamine hydrochloride and triphosgene to obtain metaxylylene diisocyanate, the reaction solution at the beginning of the reaction may be opaque colorless or white, and the reaction solution at the time when the reaction is ordinarily completed may be transparent or close to transparent in a light brown color.

For example, in the step of measuring the color and transparency of the reaction solution, the reaction solution may have a transparent light brown color.

Specifically, the reaction solution may have an L* value of 45 to 60, an a* value of 3 to 15, and a b* value of 15 to 30 in the CIE-LAB color coordinate. More specifically, the reaction solution may have an L* value of 50 to 55, an a* value of 5 to 10, and a b* value of 20 to 25 in the CIE-LAB color coordinate.

In addition, the reaction solution may have a transmittance of 60% or more, 70% or more, 80% or more, or 90% or more, for light having a wavelength of 550 nm. In addition, the reaction solution may have a haze of 20% or less, 10% or less, 5% or less, or 3% or less. Specifically, the reaction solution may have a transmittance of 70% or more for light having a wavelength of 550 nm and a haze of 10% or less. More specifically, the reaction solution may have a transmittance of 80% or more for light having a wavelength of 550 nm and a haze of 5% or less.

On the other hand, if the reaction of the metaxylylenediamine hydrochloride and triphosgene is not completed, the reaction solution may be opaque or have a precipitate, and the color may be pale, white, or colorless. In addition, if side reactions take place to a significant extent, the reaction solution may be opaque or may have a color other than light brown, for example, a dark brown or dark color.

The reaction of the diamine hydrochloride composition and triphosgene may be carried out simultaneously with the step of measuring the color and transparency of the reaction solution.

That is, while the reaction of the diamine hydrochloride composition and triphosgene is being carried out, the color and transparency of the reaction solution may be measured in real time.

In addition, for more accurate measurement, a part of the reaction solution may be collected to precisely measure the color and transparency thereof. For example, the measurement of the color and transparency of the reaction solution may be carried out by collecting a part of the reaction solution and measuring the color and transparency of the collected reaction solution.

In such event, the reaction equivalent, reaction temperature, or reaction time may be adjusted according to the color and transparency of the reaction solution. For example, the timing for terminating the reaction may be determined according to the color and transparency of the reaction solution. Specifically, the timing for terminating the reaction may come after when the reaction solution turns a transparent light brown color.

As an example, the reactor may have a viewing window, and the measurement of the color and transparency of the reaction solution may be carried out through the viewing window.

The reactor is connected to one or more stages of condensers. Once the gas generated in the reactor has been transferred to the one or more stages of condensers, the second organic solvent present in the gas may be condensed and recycled to the reactor.

The one or more stages of condensers are connected to a first scrubber and a second scrubber. The gas transferred from the reactor to the one or more stages of condensers contains hydrogen chloride gas and phosgene gas, the first scrubber may dissolve the hydrogen chloride gas in water to produce an aqueous solution, and the second scrubber may neutralize the phosgene gas with an aqueous NaOH solution.

In addition, the reactor is connected to one or more stages of distillers. The reaction solution is transferred to the one or more stages of distillers, and the one or more stages of distillers may separate the diisocyanate composition and the second organic solvent from the reaction solution.

The separated second organic solvent may be recycled for the reaction of the diamine hydrochloride composition and triphosgene.

FIG. 2 shows an example of the process equipment for the reaction of a diamine hydrochloride composition and triphosgene.

First, a first tank (T-1) is charged with a second organic solvent and triphosgene, and the temperature is maintained to be constant by refluxing hot water. The inside of a reactor (R-1) is purged with nitrogen, a second organic solvent is introduced thereto with stirring, a diamine hydrochloride composition is slowly introduced thereto, and they are stirred while the internal temperature of the reactor is maintained to be constant.

Thereafter, triphosgene in the second organic solvent is gradually introduced into the reactor (R-1) from the first tank (T-1). The introduction of triphosgene in the second organic solvent is carried out at a time or divided into two or more times. At that time, stirring is performed while the internal temperature of the reactor (R-1) is maintained to be constant. Upon completion of the introduction, an additional reaction is carried out while stirring is performed for a certain period of time. As an example, the color and transparency of the reaction solution are monitored with the naked eyes through a viewing window (G-1) provided in the reactor (R-1). As another example, the color and transparency of the reaction solution are measured with an optical device through the viewing window (G-1) provided in the reactor (R-1). The optical device may include a digital camera, a spectrometer, and optical analysis equipment.

The gas (second organic solvent, hydrogen chloride, phosgene, and the like) present inside the reactor (R-1) is transferred to a first condenser (C-1). In the first condenser (C-1), the second organic solvent is firstly condensed by cooling and recycled to the reactor (R-1), and the remaining gas is transferred to a second condenser (C-2). In the second condenser (C-2), the second organic solvent is secondly condensed by cooling and recycled to the reactor (R-1), and the remaining gas is transferred to a third condenser (C-3). In the third condenser (C-3), the second organic solvent is thirdly condensed by cooling and recycled to the reactor (R-1).

Once the second organic solvent is removed while it passes through the multi-stage condensers as described above, the remaining gas (hydrogen chloride, phosgene, and the like) is transferred to a first scrubber (S-1). In the first scrubber (S-1), hydrogen chloride gas is dissolved in water to obtain an aqueous hydrochloric acid solution and stored in a second tank (T-2), and the remaining gas is transferred to a second scrubber (S-2). In the second scrubber (S-1), phosgene (COCl₂) gas may be neutralized with an aqueous sodium hydroxide solution stored in a third tank (T-3) and removed.

The reaction solution obtained from the reactor (R-1) is sequentially transferred to a first distiller (D-1) and a second distiller (D-2). While it undergoes first and secondary distillation, the diisocyanate composition and the second organic solvent are separated from the reaction solution.

The second organic solvent separated from the reaction solution may be transferred to, and stored in, a solvent recovery apparatus (V-1). Thereafter, it may be recycled for the reaction of the diamine hydrochloride composition and triphosgene.

In addition, the diisocyanate composition separated from the reaction solution may be further subjected to filtration and drying to provide a final product.

[Process for the Preparation of an Optical Lens]

The diisocyanate composition prepared in the above embodiment may be combined with other components to prepare a composition for an optical material. That is, the composition for an optical material comprises a diisocyanate composition prepared according to the above embodiment and a thiol or an episulfide. The composition for an optical material may be used to prepare an optical material, specifically an optical lens. For example, the composition for an optical material is mixed and heated and cured in a mold to produce an optical lens. The process for preparing an optical lens or the characteristic thereof described below should be understood as a process for preparing various optical materials or the characteristic thereof that can be implemented using the diisocyanate composition according to the embodiment in addition to an optical lens.

The process for preparing an optical lens according to an embodiment comprises (1) reacting a diamine composition with an aqueous hydrochloric acid solution to obtain a diamine hydrochloride composition; (2) reacting the diamine hydrochloride composition with triphosgene to obtain a diisocyanate composition; and (3) mixing the diisocyanate composition with a thiol or an episulfide and polymerizing and curing the resultant in a mold, wherein the diisocyanate composition has a b* value according to the CIE color coordinate of 0.1 to 2.0.

The thiol may be a polythiol containing two or more SH groups. It may have an aliphatic, alicyclic, or aromatic skeleton. The episulfide may have two or more thioepoxy groups. It may have an aliphatic, alicyclic, or aromatic skeleton.

Specific examples of the thiol include bis(2-mercaptoethyl) sulfide, 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 2,3-bis(2-mercaptoethylthio)propane-1-thiol, 2,2-bis(mercaptomethyl)-1,3-propanedithiol, tetrakis(mercaptomethyl)methane, 2-(2-mercaptoethylthio)propane-1,3-dithiol, 2-(2,3-bis(2-mercaptoethylthio)propylthio)ethanethiol, bis(2,3-dimercaptopropanyl) sulfide, bis(2,3-dimercaptopropanyl) disulfide, 1,2-bis(2-mercaptoethylthio)-3-mercaptopropane, 1,2-bis(2-(2-mercaptoethylthio)-3-mercaptopropylthio)ethane, bis(2-(2-mercaptoethylthio)-3-mercaptopropyl) sulfide, bis(2-(2-mercaptoethylthio)-3-mercaptopropyl) disulfide, 2-(2-mercaptoethylthio)-3-2-mercapto-3-[3-mercapto-2-(2-mercaptoethylthio)-propylthio] propylthio-propane-1-thiol, 2,2-bis-(3-mercapto-propionyloxymethyl)-butyl ester, 2-(2-mercaptoethylthio)-3-(2-[2-[3-mercapto-2-(2-mercaptoethylthio)-propylthio] ethylthio)ethylthio)propane-1-thiol, (4R,11S)-4,11-bis(mercaptomethyl)-3,6,9,12-tetrathiatetradecane-1,14-dithiol, (S)-3-((R-2,3-dimercaptopropyl)thio)propane-1,2-dithiol, (4R,14R)-4,14-bis(mercaptomethyl)-3,6,9,12,15-pentathiaheptane-1,17-dithiol, (S)-3-((R-3-mercapto-2-((2-mercaptoethyl)thio)propyl)thio)-2-((2-mercaptoethyl)thio)propane-1-thiol, 3,3′-dithiobis(propane-1,2-dithiol), (7R,11S)-7,11-bis(mercaptomethyl)-3,6,9,12,15-pentathiaheptadecane-1,17-dithiol, (7R,12S)-7,12-bis(mercaptomethyl)-3,6,9,10,13,16-hexathiaoctadecane-1,18-dithiol, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, pentaerythritol tetrakis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), bispentaerythritol-ether-hexakis(3-mercaptopropionate), 1,1,3,3-tetrakis(mercaptomethylthio)propane, 1,1,2,2-tetrakis(mercaptomethylthio)ethane, 4,6-bis(mercaptomethylthio)-1,3-dithiane, bis(mercaptodimethylthio)ethyl)-1,3-dithiane, 2,5-bismercaptomethyl-1,4-dithiane, bis(mercaptomethyl)-3,6,9-trithiaundecan-1,11-dithiol.

Preferably, the thiol may be 2-(2-mercaptoethylthio)propane-1,3-dithiol, 2,3-bis(2-mercaptoethylthio)propane-1-thiol, 2-(2,3-bis(2-mercaptoethylthio)propylthio)ethanethiol, 1,2-bis(2-mercaptoethylthio)-3-mercaptopropane, 1,2-bis(2-(2-mercaptoethylthio)-3-mercaptopropylthio)-ethane, bis(2-(2-mercaptoethylthio)-3-mercaptopropyl) sulfide, 2-(2-mercaptoethylthio)-3-2-mercapto-3-[3-mercapto-2-(2-mercaptoethylthio)-propylthio]propylthio-propane-1-thiol, 2,2′-thiodiethanethiol, 4,14-bis(mercaptomethyl)-3,6,9,12,15-pentathiahectadecane-1,17-dithiol, 2-(2-mercaptoethylthio)-3-[4-(1-{4-[3-mercapto-2-(2-mercaptoethylthio)-propoxy]-phenyl}-1-methylethyl)-phenoxy]-propane-1-thiol, pentaerythritol tetrakis (3-mercaptopropionate), pentaerythritol mercaptoacetate, trimethanolpropanetrismercaptopropionate, glycerol trimercaptopropionate, dipentaerythritol hexamercaptopropionate, or 2,5-bismercaptomethyl-1,4-dithiane. The thiol may be any one or two or more of the exemplary compounds, but it is not limited thereto.

In addition, specific examples of the episulfide include bis(β-epithiopropylthio)methane, 1,2-bis(β-epithiopropylthio)ethane, 1,3-bis(β-epithiopropylthio)propane, 1,2-bis(β-epithiopropylthio)propane, 1-(β-epithiopropylthio)-2-(β-epithiopropylthiomethyl)propane, 1,4-bis(β-epithiopropylthio)butane, 1,3-bis(β-epithiopropylthio)butane, 1-(β-epithiopropylthio)-3-(β-epithiopropylthiomethyl)butane, 1,5-bis(β-epithiopropylthio)pentane, 1-(β-epithiopropylthio)-4-(β-epithiopropylthiomethyl)pentane, 1,6-bis(β-epithiopropylthio)hexane, 1-(β-epithiopropylthio)-5-(β-epithiopropylthiomethyl)hexane, 1-(β-epithiopropylthio)-2-[(2-β-epithiopropylthioethyl)thio] ethane, 1-(β-epithiopropylthio)-2-[[2-(2-β-epithiopropylthioethyl)thioethyl]thio] ethane, tetrakis (β-epithiopropylthiomethyl)methane, 1, 1,1-tris(β-epithiopropylthiomethyl)propane, 1,5-bis(β-epithiopropylthio)-2-(β-epithiopropylthiomethyl)-3-thiapentane, 1,5-bis(β-epithiopropylthio)-2,4-bis(β-epithiopropylthiomethyl)-3-thiapentane, 1-(β-epithiopropylthio)-2,2-bis(β-epithiopropylthiomethyl)-4-thiahexane, 1,5,6-tris(β-epithiopropylthio)-4-(β-epithiopropylthiomethyl)-3-thiahexane, 1,8-bis(β-epithiopropylthio)-4-(β-epithiopropylthiomethyl)-3,6-dithiaoctane, 1,8-bis(β-epithiopropylthio)-4,5-bis(β-epithiopropylthiomethyl)-3,6-dithiaoctane, 1,8-bis(β-epithiopropylthio)-4,4-bis(β-epithiopropylthiomethyl)-3,6-dithiaoctane, 1,8-bis(β-epithiopropylthio)-2,4,5-tris(β-epithiopropylthiomethyl)-3,6-dithiaoctane, 1,8-bis(β-epithiopropylthio)-2,5-bis(β-epithiopropylthiomethyl)-3,6-dithiaoctane, 1,9-bis(β-epithiopropylthio)-5-(β-epithiopropylthiomethyl)-5-[(2-β-epithiopropylthioethyl)thiomethyl]-3,7-ditianonane, 1,10-bis(β-epithiopropylthio)-5,6-bis[(2-β-epithiopropylthioethyl)thio]-3,6,9-trithiadecane, 1,11-bis (13-epithiopropylthio)-4,8-bis(β-epithiopropylthiomethyl)-3,6,9-trithiaundecane, 1,11-bis(β-epithiopropylthio)-5,7-bis(β-epithiopropylthiomethyl)-3,6,9-trithiaundecane, 1,11-bis(β-epithiopropylthio)-5,7-[(2-β-epithiopropylthioethyl)thiomethyl]-3,6,9-trithiaundecane, 1,11-bis(β-epithiopropylthio)-4,7-bis(β-epithiopropylthiomethyl)-3,6,9-trithiaundecane, 1,3-bis(β-epithiopropylthio)cyclohexane, 1,4-bis(β-epithiopropylthio)cyclohexane, 1,3-bis(β-epithiopropylthiomethyl)cyclohexane, 1,4-bis(β-epithiopropylthiomethyl)cyclohexane, bis[4-(β-epithiopropylthio)cyclohexyl]methane, 2,2-bis[4-(β-epithiopropylthio)cyclohexyl]propane, bis[4-(β-epithiopropylthio)cyclohexyl] sulfide, 2,5-bis(β-epithiopropylthiomethyl)-1,4-dithiane, 2,5-bis(β-epithiopropylthioethylthiomethyl)-1,4-dithiane, 1,3-bis(β-epithiopropylthio)benzene, 1,4-bis(β-epithiopropylthio)benzene, 1,3-bis(β-epithiopropylthiomethyl)benzene, 1,4-bis(β-epithiopropylthiomethyl)benzene, bis[4-(β-epithiopropylthio)phenyl] methane, 2,2-bis[4-(β-epithiopropylthio)phenyl]propane, bis[4-(β-epithiopropylthio)phenyl] sulfide, bis[4-(β-epithiopropylthio)phenyl] sulfone, and 4,4′-bis(β-epithiopropylthio)biphenyl.

The episulfide may be any one or two or more of the exemplary compounds, but it is not limited thereto. In addition, the episulfide may be a compound in which at least one of the hydrogens of its thioepoxy group is substituted with a methyl group.

The composition for an optical material may comprise the diisocyanate composition and the thiol or episulfide in a mixed state or in a separated state. That is, in the composition, they may be in a state of being compounded in contact with each other or separated from each other so as not to contact each other.

The composition for an optical material may comprise the thiol or episulfide and the diisocyanate composition at a weight ratio of 2:8 to 8:2, 3:7 to 7:3, or 4:6 to 6:4.

A catalyst, a chain extender, a crosslinking agent, an ultraviolet stabilizer, an antioxidant, an anti-coloring agent, a dye, a filler, a release agent, and the like may be further added depending on the purpose when the composition for an optical material and an optical lens are prepared.

The thiol or episulfide is mixed with a diisocyanate composition and other additives, which is defoamed, injected into a mold, and gradually polymerized while the temperature is gradually elevated from low to high temperatures. The resin is cured by heating to prepare an optical lens.

The polymerization temperature may be, for example, 20° C. to 150° C., particularly 25° C. to 120° C. In addition, a reaction catalyst, which is conventionally used in the production of polythiourethane, may be employed in order to control the reaction rate. Specific examples of the reaction catalyst are as exemplified above.

In addition, if required, the optical lens thus prepared may be subjected to physical or chemical treatment such as anti-reflection coating, hardness, enhancements in abrasion resistance and chemical resistance, anti-fogging, surface polishing, antistatic treatment, hard coat treatment, anti-reflection treatment, and dyeing treatment.

The optical lens prepared by the above process has excellent optical properties such as transparency, refractive index, and yellow index. For example, the optical lens may have a refractive index of 1.55 or more, specifically a refractive index of 1.55 to 1.77. Alternatively, the optical lens may have a refractive index of 1.6 or more, specifically a refractive index of 1.6 to 1.7.

In addition, the optical lens may have an Abbe number of 30 to 50, specifically 30 to 45 or 31 to 40. In addition, the optical lens may have a light transmittance of 80% or more, 85% or more, or 87% or more, which may be a total light transmittance.

In addition, the optical lens may have a yellow index (Y.I.) of 30 or less, 25 or less, or 20 or less, for example, 1 to 25 or 10 to 20. Specifically, the optical lens may have a transmittance of 90% or more and a yellow index of 20 or less.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, more specific embodiments are illustrated, but the present invention is not limited thereto.

Examples 1 to 4, and Comparative Examples 1 and 2: Preparation of a Diisocyanate Composition

Step (1): Preparation of a Diamine Hydrochloride Composition

A reactor was charged with 1,009.4 g (9.46 moles) of an aqueous solution of 35% hydrochloric acid having a content of Fe ions as shown in Table 2 below, followed by lowering the internal temperature of the reactor to 15° C. with stirring. While the temperature of the reactor was maintained at 60° C., 600.0 g (4.4 moles) of m-XDA was introduced for 1 hour. Upon completion of the introduction, the internal temperature of the reactor was lowered to 10° C., and it was stirred for 1 hour. Thereafter, 1,320.0 g of tetrahydrofuran (THF) was introduced, and the internal temperature of the reactor was lowered to −5° C., followed by stirring for 1 hour. Upon completion of the reaction, the diamine hydrochloride composition containing m-XDA.2HCl was separated by vacuum filtration using a filter, and the filtered tetrahydrofuran was recovered for reuse. The separated diamine hydrochloride composition was dried under vacuum at 90° C. and 0.5 torr to remove the residual solvent and water.

If necessary, the dried diamine hydrochloride composition was washed with dichloromethane at 0 to 5° C., dried under vacuum at 90° C. to 100° C. and 0.1 torr, and used in the next step.

Step (2): Preparation of a Diisocyanate Composition

Reactor A was charged with 800 g of the diamine hydrochloride composition prepared above and 3,550 g of ODCB, which was heated at about 125° C. with stirring. Reactor B was charged with 950 g of triphosgene (BTMC) and 800 g of ODCB, which was stirred at about 60° C. for dissolution. While the temperature was maintained at 125° C. so as not to precipitate, it was added dropwise to Reactor A over 24 hours.

Upon completion of the dropwise addition, it was stirred for 4 hours. Upon completion of the reaction, nitrogen gas was blown into the solvent with bubbling at 125° C. to degas. Thereafter, it was cooled to 10° C., and the remaining solids were filtered using celite. The organic solvent (ODCB) was removed, and distillation was carried out to obtain a diisocyanate composition containing m-XDI. Here, the removal of the organic solvent was carried out for 8 hours at a pressure of 0.5 torr or less and a temperature of 60° C. In addition, the distillation was carried out for 10 hours at a temperature of 120° C. and a pressure of 0.5 torr or less.

Example 5

Step (1): Preparation of a Diamine Hydrochloride Composition

Reactor 1 was charged with 1,009.4 g (9.46 moles) of an aqueous solution of 35% hydrochloric acid having a content of Fe ions as shown in Table 2 below, followed by lowering the internal temperature of Reactor 1 to 15° C. with stirring. While the temperature of Reactor 1 was maintained at 50° C. or lower, 627.0 g (4.4 moles) of H6XDA was introduced for 1 hour. Upon completion of the introduction, the internal temperature of the reactor was lowered to 10° C., and it was stirred for 1 hour. The internal temperature of Reactor 2 to which 2,640.0 g of diethyl ether had been charged was lowered to −5° C. The mixture in Reactor 1 was slowly added dropwise to Reactor 2 at 0° C. or lower.

Upon completion of the addition, the diamine hydrochloride composition containing H6XDA.2HCl was separated by vacuum filtration using a filter, and the filtered diethyl ether was recovered for reuse. Thereafter, the separated diamine hydrochloride composition was dried under vacuum at 90° C. and 0.5 torr to remove the residual solvent and water.

Step (2): Preparation of a Diisocyanate Composition

Reactor A was charged with 823 g of the diamine hydrochloride composition prepared above and 3,550 g of ODCB, which was heated at about 125° C. with stirring. Reactor B was charged with 950 g of triphosgene (BTMC) and 800 g of ODCB, which was stirred at about 60° C. for dissolution. While the temperature was maintained at 125° C. so as not to precipitate, it was added dropwise to Reactor A over 24 hours. Upon completion of the dropwise addition, it was stirred for 3 to 4 hours. Upon completion of the reaction, nitrogen gas was blown into the solvent with bubbling at 125° C. to degas. Thereafter, it was cooled to 10° C., and the remaining solids were filtered using celite. The organic solvent (ODCB) was removed, and distillation was carried out to obtain a diisocyanate composition containing H6XDI. Here, the removal of the organic solvent was carried out for 8 hours at a pressure of 0.5 torr or less and a temperature of 60° C. In addition, the distillation was carried out for 10 hours at a temperature of 120° C. and a pressure of 0.5 torr or less.

Example 6

Step (1): Preparation of a Diamine Hydrochloride Composition

A reactor was charged with 1,009.4 g (9.46 moles) of an aqueous solution of 35% hydrochloric acid having a content of Fe ions as shown in Table 2 below, followed by lowering the internal temperature of the reactor to 15° C. with stirring. While the temperature of the reactor was maintained at 50° C. or lower, 490.1 g (4.4 moles) of HDA was introduced for 1 hour. Upon completion of the introduction, the internal temperature of the reactor was lowered to 10° C., and it was stirred for 1 hour. Thereafter, 1,320.0 g of tetrahydrofuran was introduced, and the internal temperature of the reactor was lowered to −5° C., followed by stirring for 1 hour. Upon completion of the reaction, the diamine hydrochloride composition containing HDA.2HCl was separated by vacuum filtration using a filter, and the filtered tetrahydrofuran was recovered for reuse. Thereafter, the separated diamine hydrochloride composition was dried under vacuum at 90° C. and 0.5 torr to remove the residual solvent and water.

Step (2): Preparation of a Diisocyanate Composition

Reactor A was charged with 723 g of the diamine hydrochloride composition prepared above and 3,550 g of ODCB, which was heated at about 125° C. with stirring. Reactor B was charged with 950 g of triphosgene (BTMC) and 800 g of ODCB, which was stirred at about 60° C. for dissolution. While the temperature was maintained at 125° C. so as not to precipitate, it was added dropwise to Reactor A over 24 hours. Upon completion of the dropwise addition, it was stirred for 3 to 4 hours. Upon completion of the reaction, nitrogen gas was blown into the solvent with bubbling at 125° C. to degas. Thereafter, it was cooled to 10° C., and the remaining solids were filtered using celite to obtain a diisocyanate composition containing HDI. Thereafter, the organic solvent in the diisocyanate composition was removed, and distillation was carried out. Here, the removal of the organic solvent was carried out for 8 hours at a pressure of 0.5 torr or less and a temperature of 60° C. In addition, the distillation was carried out for 10 hours at a temperature of 120° C. and a pressure of 0.5 torr or less.

Example 7

Step (1): Preparation of a Diamine Hydrochloride Composition

Reactor 1 was charged with 1,009.4 g (9.46 moles) of an aqueous solution of 35% hydrochloric acid having a content of Fe ions as shown in Table 2 below, followed by lowering the internal temperature of Reactor 1 to 15° C. with stirring. While the temperature of Reactor 1 was maintained at 50° C. or lower, 812.0 g (4.4 moles) of IPDA was introduced for 1 hour. Upon completion of the introduction, the internal temperature of the reactor was lowered to 10° C., and it was stirred for 1 hour. The internal temperature of Reactor 2 to which 2,640.0 g of diethyl ether had been charged was lowered to −5° C. The mixture in Reactor 1 was slowly added dropwise to Reactor 2 at 0° C. or lower. Upon completion of the addition, the diamine hydrochloride composition containing IPDA.2HCl was separated by vacuum filtration using a filter, and the filtered diethyl ether was recovered for reuse. Thereafter, the separated diamine hydrochloride composition was dried under vacuum at 90° C. and 0.5 torr to remove the residual solvent and water.

Step (2): Preparation of a Diisocyanate Composition

Reactor A was charged with 984 g of the diamine hydrochloride composition prepared above and 3,550 g of ODCB, which was heated at about 125° C. with stirring. Reactor B was charged with 950 g of triphosgene (BTMC) and 800 g of ODCB, which was stirred at about 60° C. for dissolution. While the temperature was maintained at 125° C. so as not to precipitate, it was added dropwise to Reactor A over 24 hours. Upon completion of the dropwise addition, it was stirred for 3 to 4 hours. Upon completion of the reaction, nitrogen gas was blown into the solvent with bubbling at 125° C. to degas. Thereafter, it was cooled to 10° C., and the remaining solids were filtered using celite to obtain a diisocyanate composition containing IPDI. Thereafter, the organic solvent in the diisocyanate composition was removed, and distillation was carried out. Here, the removal of the organic solvent was carried out for 8 hours at a pressure of 0.5 torr or less and a temperature of 60° C. In addition, the distillation was carried out for 10 hours at a temperature of 120° C. and a pressure of 0.5 torr or less.

Comparative Example 3

The procedures of Step (1) of Example 5 were repeated, except that a diamine hydrochloride composition using an aqueous solution of 35% hydrochloric acid having a content of Fe ions as shown in Table 2 below was prepared, and a diisocyanate composition was prepared according to the procedures of Step (2) of Example 5.

Comparative Example 4

The procedures of Step (1) of Example 6 were repeated, except that a diamine hydrochloride composition using an aqueous solution of 35% hydrochloric acid having a content of Fe ions as shown in Table 2 below was prepared, and a diisocyanate composition was prepared according to the procedures of Step (2) of Example 5.

Comparative Example 5

The procedures of Step (1) of Example 7 were repeated, except that a diamine hydrochloride composition using an aqueous solution of 35% hydrochloric acid having a content of Fe ions as shown in Table 2 below was prepared, and a diisocyanate composition was prepared according to the procedures of Step (2) of Example 5.

<Preparation of an Optical Lens>

As shown in Table 1 below, the diisocyanate composition (main component: m-XDI, H6XDI, HDI, or IPDI) prepared in the Examples or the Comparative Examples, 5,7-dimercaptomethyl-1,11-dimercapto-3,6-trithiaundecane (BET) as a polythiol, and a tin-based catalyst as an additive were uniformly mixed and defoamed at 600 Pa for 1 hour to prepare a polymerizable composition.

The polymerizable composition was filtered through a 3-μm Teflon filter and injected into a glass mold assembled with an adhesive tape. The polymerizable composition injected into the mold was subjected to a first polymerized at a temperature of 10° C. to 35° C. for 3 to 9 hours, a second polymerization at a temperature of 35° C. to 60° C. for 3 to 9 hours, and a third polymerization at a temperature exceeding 60° C. for 2 to 7 hours. Upon the polymerization, the plastic molded article (optical lens) was released from the mold and subjected to further curing at 130° C. for 2 hours.

TABLE 1 Polymerizable composition Diisocyanate composition Polythiol Part by Main (BET) Additive Type weight component Part by weight Catalyst Ex. 1 50.7 m-XDI 49.3 0.01 Ex. 2 50.7 m-XDI 49.3 0.01 Ex. 3 50.7 m-XDI 49.3 0.01 Ex. 4 50.7 m-XDI 49.3 0.01 Ex. 5 48.6 H6XDI 51.4 0.05 Ex. 6 48.6 HDI 51.4 0.05 Ex. 7 48.2 IPDI 54.8 0.05 C. Ex. 1 50.7 m-XDI 49.3 0.01 C. Ex. 2 50.7 m-XDI 49.3 0.01 C. Ex. 3 48.6 H6XDI 51.4 0.05 C. Ex. 4 48.6 HDI 51.4 0.05 C. Ex. 5 48.2 IPDI 54.8 0.05

<Evaluation Method>

The Examples and the Comparative Examples were evaluated as follows.

(1) Measurement of b*

The b* value was measured using a spectrophotometer (Colormate, Sinko Corporation) according to ASTM E313-96. A liquid sample was filled in a quartz cell having a thickness of 10 mm, and a solid sample was dissolved in an organic solvent (ODCB) at 8% by weight. The lower the b* value, the better the color.

(2) Refractive Index (Nd20)

The solid-phase refractive index (nd20) was measured at 20° C. using an Abbe refractometer DR-M4 (Atago Co.).

(3) Yellow Index (Y.I.) and Light Transmittance

An optical lens was prepared in the form of a cylinder with a radius of 16 mm and a height of 45 mm. Light was transmitted in the height direction to measure yellow index (Measurement Standard: ASTM E313-96) and transmittance (Measurement Standard: ISO 73468). (4) Stria

A lens having a diameter of 75 mm with −2.00 and −8.00 D was prepared. Light from a mercury lamp as a light source was transmitted through the lens. The transmitted light was projected onto a white plate, and the presence or absence of contrast was visually checked to determine the generation of striae.

-   -   (5) ICP-MS measurement     -   Analysis device: ICP-OES (Inductively Coupled Plasma-Optical         Emission Spectrometer)     -   Device detail: 730ES of Agilent     -   Light source: Axially viewed Plasma system     -   Detector: 167-785 nm wavelength CCD (charge coupled device)         detector     -   Sample pretreatment: for a liquid sample, 2 g thereof was         sonicated in 18 g of water for 1 hour, and the aqueous layer was         collected. For a solid sample, a solution in which 0.2 g thereof         was dissolved in 19.8 g of water was prepared.

The results are shown in the tables below.

TABLE 2 Content of Diisocyanate composition Fe ions in Diisocyanate the aqueous Diamine content hydrochloric hydrochloride (% by weight) acid composition Distillation Before After solution Yield yield distil- distil- (ppm) (%) b* (%) lation lation b* Ex. 1 0.1 92 0.6 91 99.1 99.9 0.6 Ex. 2 0.6 85 1.8 90 98.9 99.9 0.5 before washing 1.1 after washing Ex. 3 0.4 91 1.5 91 99.0 99.9 1.8 Ex. 4 1.0 91 2.2 90 98.5 99.9 1.0 before washing 1.3 after washing Ex. 5 0.1 91 0.5 91 99.1 99.9 0.5 Ex. 6 0.1 90 0.6 91 99.1 99.9 0.4 Ex. 7 0.1 90 0.5 91 99.1 99.9 0.5 C. Ex. 1 0.6 91 1.8 87 98.2 99.6 2.5 C. Ex. 2 1.0 92 2.2 87 98.0 99.5 2.8 C. Ex. 3 0.6 91 1.7 86 98.2 99.6 2.5 C. Ex. 4 0.6 90 1.8 85 98.2 99.6 2.4 C. Ex. 5 0.6 91 1.8 88 98.2 99.6 2.2

TABLE 3 Diisocyanate Optical lens composition Refractive b* Stria Transmittance Y.I. index Ex. 1 0.6 None 90 18 1.669 Ex. 2 0.5 None 91 21 1.669 Ex. 3 1.8 None 90 22 1.669 Ex. 4 1.0 None 91 21 1.669 Ex. 5 0.5 None 90 20 1.623 Ex. 6 0.4 None 91 20 1.624 Ex. 7 0.5 None 90 21 1.596 C. Ex. 1 2.5 None 90 25 1.669 C. Ex. 2 2.8 None 88 28 1.669 C. Ex. 3 2.5 None 89 26 1.623 C. Ex. 4 2.4 None 89 27 1.624 C. Ex. 5 2.2 None 90 26 1.596

As can be seen from the above tables, the optical lenses prepared from the diisocyanate compositions having a b* value in the range of 0.1 to 2.0 as in Examples 1 to 7 were all excellent in terms of stria, transmittance, yellow index, and refractive index. In contrast, yellowing took place in the optical lenses prepared from the diisocyanate composition having a b* value falling outside the range of 0.1 to 2.0 as in Comparative Examples 1 to 5. 

1. A process for preparing a diisocyanate composition, which comprises: (1) reacting a diamine composition with an aqueous hydrochloric acid solution to obtain a diamine hydrochloride composition; and (2) reacting the diamine hydrochloride composition with triphosgene to obtain a diisocyanate composition, wherein the diisocyanate composition has a b* value according to the CIE color coordinate of 0.1 to 2.0.
 2. The process for preparing a diisocyanate composition of claim 1, wherein the content of Fe ions in the aqueous hydrochloric acid solution is 0.5 ppm or less.
 3. The process for preparing a diisocyanate composition of claim 1, wherein the diamine hydrochloride composition has a b* value according to the CIE color coordinate of 1.5 or less when dissolved in water at a concentration of 8% by weight.
 4. The process for preparing a diisocyanate composition of claim 3, wherein the b* value according to the CIE color coordinate of the diamine hydrochloride composition is adjusted by washing it with a solvent having a polarity of 5.7 or less.
 5. The process for preparing a diisocyanate composition of claim 1, which further comprises measuring the b* value according to the CIE color coordinate of the diamine hydrochloride composition.
 6. The process for preparing a diisocyanate composition of claim 1, wherein the diisocyanate composition is obtained by distillation after the reaction of the diamine hydrochloride composition and triphosgene, and the distillation comprises distillation of diisocyanate at a temperature of 100° C. to 130° C. and a pressure of 2.0 torr or less.
 7. A process for preparing an optical lens, which comprises: (1) reacting a diamine composition with an aqueous hydrochloric acid solution to obtain a diamine hydrochloride composition; (2) reacting the diamine hydrochloride composition with triphosgene to obtain a diisocyanate composition; and (3) mixing the diisocyanate composition with a thiol or an episulfide and polymerizing and curing the resultant in a mold, wherein the diisocyanate composition has a b* value according to the CIE color coordinate of 0.1 to 2.0.
 8. The process for preparing an optical lens of claim 7, wherein the optical lens has a transmittance of 90% or more and a yellow index (Y.I.) of 20 or less. 